1. Field of the Invention
The invention relates to a fabric tensioning device for stretching work fabric in the sewing location of a sewing machine.
2. Description of Related Art
Devices for tensioning a piece of tube-like fabric, such as material for socks and wrist bands, using a cylindrical frame are used in embroidering on a sewing machine. One of such a fabric tensioning devices is disclosed in International Patent Publication Number WO00/53836. This device has a cylindrical frame 101 which is placed to cover the outside of the cylinder bed (not shown) of the sewing machine as shown in FIG. 11. The cylindrical frame 101 includes a sewing window 102 for exposing the sewing area of the cylinder bed, a core material clamping member 105 for clamping down thick core material C against the cylindrical frame 101, and a fabric clamping member 103 for clamping down the fabric and the core material C against the cylindrical frame 101. The fabric is arranged to cover the core material C which is arranged to cover the sewing window 102. The core material clamping member 105 is formed in a rectangular shape with a closed front end so that the core material C can be clamped in one stroke. The core material clamping member 105 is attached to the cylindrical frame 101 to be able to open and close vertically.
However, with this fabric tensioning device, the core material clamping member 105 clamps down the core material C from the rear to the front simultaneously on both the left and right side of cylindrical frame 101. Therefore, the cylindrical shape of the core material C tends to be lower on the rear side or cause a localized deformation, thereby essentially making it difficult to properly fit the entire core material C around the circumference of cylindrical frame 101. Thus, the core material C is difficult to set since it is necessary to straighten or restretch the stretched core material C.
The present invention provides a fabric tensioning device for a sewing machine that can solve the abovementioned problem by holding down the core material on the left side and the right side individually so that it can be easily stretched in a properly aligned manner on the outer periphery of the cylindrical frame.
In order to solve the abovementioned problem, the fabric tensioning device according to the present invention comprises a cylindrical frame having a sewing window, a core material clamping member for clamping down a core material against the cylindrical frame and a fabric clamping member for clamping down the fabric and the core material against the cylindrical frame. The core material covers the sewing window, and the fabric covers the core material. The fabric clamping member is able to open or close against the cylindrical frame. The core material clamping member consists of two members provided with one on each side of the left and right sides of the cylindrical frame. The two members extend in the axial (front and rear) direction and can open or close against the cylindrical frame independently.
The core material clamping members can open or close in either a vertical direction or a lateral direction. However, the two core material clamping members can be mounted on the left and right sides of the cylindrical frame at the rear ends of the two clamping members respectively. Therefore, the two core material clamping members can open or close their respective front end in the lateral direction in order to make it easier to stretch the core material at the same height on the front and rear against the cylindrical frame. Furthermore, tighteners can be provided protrusively on the outer surface of the cylindrical frame extending along the left and right edges of the sewing window in order to prevent the core material from slackening or deforming. A core material clamping member can be provided under each tightener.
The core material clamping member does not have a specific shape requirement. The core material clamping member can be made of a long rod or a strip extending in the axial (front and rear) direction. Several clamps along the axial direction can be provided on the inside of the core material clamping member so that the oblong core material clamping member can press down various parts of the core material. Additionally, a temporary latch can engage the cylindrical frame at the front end of the core material clamping member in order to hold the shape of the core material until the work fabric is stretched.
The fabric clamping material does not have a specific constitution requirement. The fabric clamping material can have two fabric clamps, one on each side of the left and right sides of the fabric clamping member, and a band that tightens the fabric clamping member and the core material clamping members together against the cylindrical frame. The two fabric clamps can face the core material clamping member from the outside. Slip guards made of processed fabric can be provided on the outer surface of the core material clamping members.